Studies on the Flavors of Roast Barley (Mugi-Cha): Part V. Further Separation and Identification of Carbonyl Compounds

Five weakly acidic carbonyl compounds and two neutral carbonyl compounds were newly isolated as their 2,4-dinitrophenylhydrazones besides the previously reported compounds by using column and thin-layer chromatographies. These compounds were characterized and identified by their IR, UV and MS spectra and the mixed melting points test. The newly isolated and identified compounds were as follows; weakly acidic carbonyl compounds: 2-pyrrolealdehyde, vanillin, p-hydroxybenzaldehyde, syringaldehyde, proto-catechuic aldehyde, neutral carbonyl compounds: glyoxal, 5-hydroxymethylfurfural. These compounds, particularly vanillin, protocatechuic aldehyde, 2-pyrrolealdehyde and 5-hydroxymethylfurfural, appeared to be concerned with the flavor of roast barley (Mugi-Cha).